New method of manufacturing acrylic fibers and the related products



United States Patent US. Cl. 264210 1 Claim ABSTRACT 0F THE DISCLOSURE Amethod for producing an acrylic fiber in which a spinning solutioncontaining at least 85% (Wt) of polyacrylonitrile and zinc chloride ispun into an aquagel tow which is then washed free of the zinc chloride.The washed tow is then contacted with an aqueous emulsion containing anoiling agent after which the tow is dried, heat-stretched and theneither heat-relaxed or heat-set.

The present invention relates to an improved process of spinning andafter-treatment for the production of acrylonitrile polymer fibers andmore particularly to the preparation of acrylic regular and shrinkablefibers of improved compositons. It has particular reference to thepreparation of such acrylic fibers that their softness andanti-electrostatic property are excellent and maintainedsemi-permanently and that their knitted and woven goods give anexcellent hand and have a high resilience comparable to that of woolgoods. Another aspect of the invention is to facilitate the heat-stretchand heat-relexation in the process of spinning and after-treatment forthe production of acrylic fibers by using the spinning dope composed onan acrylonitrile polymer containing at least 85 weight percent ofpolymerized acrylonitrile and an aqueous salt solvent.

The method of the present invention consists of the following roceduresin the process of producing acrylic fibers from the spinning solutioncomposed of an acrylic polymer containing at least 85 weight percent ofpolymerized acrylonitrile and an aqueous salt solvent such as aqueousconcentrated solution mainly of zinc chloride, sodium thiocyanate orcalcium thiocyanate.

(a) spinning said acrylic polymer into an aquagel tow of filament andwashing the aqueogel tow (to be conrued herein as inclusive filament)until substantially free of said solvent salt:

(b) contacting the washed aquagel tow of which fiber structure issubstantially in an un-oriented condition with an aqueous emulsioncontaining an oiling agent or oiling agents selected from thesurfactants of anionic, cationic, non-ionic and amphoteric types, so asto subject said aquagel tow to absorbing at least 1.5 weight percent intotal of said oiling agent (to be construed herein as inclusive mixtureof a plurality of agents) based on the resultant fiber in dry state; and

(c) subsequently drying said aquagel tow containing said oiling agent,heat-stretching the partially or substantially dried tow andheat-relaxing or heat-setting the stretched two.

As well known oiling treatment in the process of acrylic fiberproduction has been usually done for the heatstretched or heat-stretchedand heat-relaxed fibers of which structure has been in substantially orat least partically oriented condition. The most part of the oilingagent adhered to the fiber is present on the fiber surface and can beremoved easily with a hot alcohol-benzene mixture. The amount of theoiling agent to be added has 3,485,913 Patented Dec. 23, 1969 beenusually controlled to be in the range of 0.2-0.6 weight percent based onthe dried fiber. Since the object of such an oiling treatment has beenmainly to improve the physical property of fiber surface such asanti-electrostatic property and friction coetficient, there has been nopractical demand for permeating a considerable amount of an oiling agentover 1 weight percent into fiber structure. In fact, with respect to theuse of oiling agent in synthetic fiber industry, and considerable effectother than that of improving the practical property of fiber surface hasbeen scarcely expected.

Contrary to the ordinary method of oiling treatment mentioned above thepresent invention is characterized by the facts that an oiling treatmentis carried out for the aquagel tow which has not yet been heat-stretchedand is in the condition of substantially Lin-oriented fiber structureand that the content of the oiling agent absorbed by the aquagel tow iscontrolled to be at least 1.5 weight percent based on the product fiberin its dry state. In this case, the oiling treatment is usually done bysubjecting said aquagel tow to intimate contact with an aqueous emulsionof a synthetic surfactant, and the tow can absorb a considerable amountof the surfactant, for a very short time below one minute, due to itsun-oriented aquagel fiber structure. The absorbed surfactant will bepermeated into the aquagel fiber structure to form an acrylic fiber of anew composition.

The amount of the surfactant to be absorbed can be easily controlled byselecting or adjusting the surfactant concentration of the aqueousemulsion, the emulsion temperature and the contacting time of theaquagel tow with the emulsion, although the affinity or absorptiontendency of the surfactant to said aquagel acrylic fibers is oftendependent upon the chemical compositon and molecular weight of thesurfactant.

The present invention is based on the un-expected findings that such aspecial oiling treatment as mentioned above facilitates the subsequentheat-stretching and heatrelaxation and that the knitted and woven goodsmade from the acrylic fibers thus obtained given an excellent hand havea high resilience comparable to that of wool goods and keep their goodhandling property for a long time.

According to the present method, the acrylic tow subjected to absorptionof a considerable amount of surfactant easily heat-stretched at a lowertemperature and or to a higher extent than that formed without saidoiling treatment, even when the tow is substantially dried and thenheat-stretched in dry air. Especially, a marked effect of such absorbedsurfactant is exhibited in relaxing the heat-stretched tow in heated airor steam under atmospheric pressure, is. with increasing the absorptioncontent of surfactant in the fiber, the maximum shrinkage in relaxationat a given temperature and for a given period is considerably increasedor the relaxation of a given shrinkage can be carried out at a lowertemperature or in a shorter period.

Several examples of those effects are shown in Table 2 and Table 3.

Also, it is surprised to have found that the acrylic fibers producedthrough the spinning and after-treatment process according to thepresent invention are more bulky in hand than those produced by priorarts and that the knitted and woven goods made from the acrylic fibersproduced by the present method give an excellent hand and have a highresilience comparable to or equal to that of wool goods and show only anegligible deterioration in their quality related to the hand even afterseveral cycles of practical washing and drying, which are superior tothose made from other acrylic fibers. In the present method, almost ofthe surfactant absorbed into the aquagel fiber structure is irreversiblyfixed by drying the resultant aquagel fiber in hot air or byheat-stretching the aquagel fiber at temperatures over about 80 C.,which can not be extracted with hot alcohol-benzene mixture. Such afixed surfactant is called as inner oil hereafter in this specification.The above mentioned effects of the present invention will be consideredto be attributed directly or indirectly to the presence of such inneroil. On the other hand, in the case of ordinary methods of acrylic fiberproduction, an aquagel tow is heatstretched (and is necessaryheat-relaxed) to have a substantially or at least partially orientedfiber structure and then subjected to an oiling treatment so as to have0.2- 0.6 weight percent of a surfactant (based on the dried productfiber), so that most of the surfactant adhered will be present on thefiber surface. Such an oiling agent can be washed out easily with a hotalcohol-benzene mixture, which is called as surface oil for shorthereafter. Table 1 shows some typical results on the inner oil andsurface oil for the acrylic fibers produced by the present invention andby the prior art, where the amount of the inner oil was estimated as thedifference between those of the total oil and the surface oil. Theamount of the total oil was estimated from the measurement of the trueconsumption of the surfactant per unit weight of the product fiber, withcorrecting the material loss accompanied with the experiment, and theamount of the surface oil measured by an extraction method with a hotalcohol-benzene (1:2) mixture.

As shown in Table l, the amounts of surface oil according to the presentmethod is in the same range of or not considerably different from thosefor the fibers produced through an ordinary procedure of oilingtreatment, which will be suitable for making spun yarns and filamentyarns.

The inner oil has been found to cause no trouble in the processes ofyarn spinning knitting and weaving.

4 steam which was under atmospheric pressure and overheated to a hightemperature near 240 C. It is clear from these results that both TABLE 2Maximum heat Total oil stretching ratio. Sample (wt. percent) percentTABLE 3 Sample Maximum shrinkage, percent A-l B-l .14 B-2 3O B3 themaximum ratio of heat-stretching and the maximum shrinkage ofheat-relaxation subsequent to the stretching increase considerably withincreasing the amount of total oil or strictly speaking the inner oil.

Practically, the heat-stretching over 4 times at a temperature between100180 C. and the subsequent heatrelaxation at a temperature over 150 C.will be preferable for producing the acrylic fibers of high bulkiness aswell as good mechanical property.

The characteristic in quality of the knitted and woven goods made fromthe acrylic fibers produced by the present invention has been describedalready in this specification. However, such quality expressions asexcellent hand and high resilience comparable to that of Wool goods arenot quantitative but rather subjective and sensory. It is thereforedesirable to provide a testing method by which the effect of the presentmethod on quality of the end-used products may be numerically estimated.Since there has been no instrumental method prior art).

The product fibers obtained through the present method can be,therefore, subjected directly to the subsequent processes such as towcutting, Turbo processing and yarn spinning. It may be often found thatthe amount of the surface oil resulting from the application of thepresent method will be not so enough that the product fiber can bedirectly supplied to yarn spinning machines to form spun yarns of goodquality. In such cases, the two may be contacted again, after theheat-stretching and heat-relaxation, with an aqueous dilute emulsion ofan oiling agent so as to increase the resultant amount of the surfaceoil up to the range suitable for yarn spinning.

As described before, the heat-stretch to be applied after drying anaquagel acrylic fiber and the subsequent heat-relaxation are facilitatedwhen the fiber to be heatstretched has a considerable amount of inneroil. Some examples of the effect are shown in Table 2 and Table 3.

Table 2 shows an experimental result on the relationship between thetotal oil content and the maximum heat-stretching ratio, where theacrylic tow samples were prepared by a wet-spinning method using anaqueous zinc chloride solvent and dried in hot-air before theheatstretching experiment. Table 3 represents the maximum shrinkagemeasured for each of the heat-stretched tows, corresponding to each ofthe experimental numbers in Table 2, where the heat-relaxation wascarried out in a of testing by which the hand and resilience of knittedand woven goods can be quantitatively detected, the present inventorsapplied a sensory inspection by a group of specialists having muchexperience on the quality test of fiber goods.

Its procedure and a typical inspection result on the effect of thepresent method will be described in Example 2 in this specification.

The present inventors have also found that a desired shrinkable fibercan be effectively manufactured by subjecting the acrylic regular towmade through the method as referred to above to some subsequenttreatments.

As well known, acrylic shrinkable fibers can be manufactured by aprocess in which an acrylic regular tow is heat-stretched again in itsdry state (hereafter this heat-stretch is called as the second stretchto discriminate it from the heat-stretch applied in the process ofproducing the regular tow), and then immediately cooled under tension inair stream, and if necessary subjected to cutting. Their shrinkage,which is measured as the degree of their shrinking in fiber length inboiling Water or in steam at C., tends to increase with increasing thesecond stretching ratio, but increase in the ratio results in decreaseof the knot strength and knot elongation of the resultant fibers, whichis not a desirable tendency from the viewpoint of manufacturing goodshrinkable yarns. Since industrial spinning operation with a flat orroller carding machine will demand a lower limit of their knot strengthor knot elongation in order to produce good shrinkable yarns, there willbe an upper limit of the second stretching ratio to be applicable andconsequently their practical shrinkage will be limited.

In the case of the acrylic regular tows produced by a wet-spinningmethod using an aqueous salt solvent such as an aqueous concentratedsolution of zinc chloride, thiocyanate or nitric acid, the fiber knotstrength and knot elongation tend to more decrease by the secondstretching than those of the acrylic tows produced using an organicsolvent such as dimethyl formamide, so that there has been a demand forany improved method by which the shrinkable fiber of a given shrinkagecan be produced at a smaller ratio of the second stretch. The presentmethod has been found to meet such a demand. The shrinkage in percent ofthe shrinkable fiber manufactured from the regular tow produced by thepresent method is higher by 210% than those of the usual shrinkablefibers when all the conditions of the second stretching are fixedconstant. For example, when the second stretch of 1.31 times wasapplied, the shrinkage was 14-15% for the shrinkable staple made fromthe acrylic tow with the present invention but in the range of 9-12% forthose made from the acrylic tow produced in accordance with the priorart. For the second stretch ranging 1.4-1.5 times, the shrinkablestaples of 21-24% shrinkage and 1.5-1.6 grams per denier of knotstrength could be obtained from the acrylic tow with the presentinvention while for the shrinkable staples from the above ordinary towsthe shrinkage was 14-16% In making acrylic shrinkable fibers the presentinventors have found that an application of a weak relaxation with steamis very much effective to improve the uniformity of shrinkage of theproduct fibers although their shrinkage is lowered a little depending onthe degree of the applied relaxation.

This result Will be very important, because the variance in yarnshrinkage of shrinkable yarns depends largely upon the variance inshrinkage of the material fiber. The copulation standard deviation ofshrinkage for a lot of acrylic shrinkable fibers is markedly decreasedby applying a Weak steam relaxation in the range of 2-6% to the towsubjected to the second stretch. For example, with respect to theacrylic shrinkable staple manufactured under the second stretch of 1.4times, the mean shrinkage percent and (7' were respectively 25% and 3.1%without undergoing the above-mentioned relaxation but were respectively21% and very 0.9% after applied the steam relaxation of 4%: also, in thecase of the second stretch of 1.5 times, the mean shrinkage and 6 wererespectively 30% and 3.3% Without the treatment but respectively 24% andonly 1.4% after 6% relaxation. In those experiments the material towsproduced by the present invention contained 3.5 weight percent of inneroil.

The surfactants usable for the present invention are of cationic,anionic, non-ionic or amphoteric type. Among of cationic surfactants,there may be alkyl amine acetate, acetate, alkyl pyridium chloride,alkyl trimethyl ammonium chloride, N-alkyl-N-ethyl morpholiniumethosulfate, diethanolamine alkyl ester and its neutralizationcompounds, bis N,N'-ethyl aminoethyl alkylamide, alkyl dimethyl benzylammonium chloride and polyoxyethylene alklyl amine, an alkyl radical ofsaid cationic compounds preferably having 8 to 18 carbon atoms. Among ofanionic surfactants, there may be sodium alkyl sulfate, polyoxyethylenealkyl sulfate, alkyl phos phate sodium dialkyl sulfosuccinate, sodiumalkyl-N- methyl lauride and N-methyl alkyl glycine, an alkyl radical ofsaid anionic compounds preferably having to 20 carbon atoms. Asnon-ionic surfactants, may be used polyoxyethylene alkyl ether,polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester,polyoxyethylene alkyl amine, polyoxyethylene alkyl amide,polyoxyethylene alkyl amino amide, sorbitan mono-alkylate, glycerolmono-alkylate or condensation compounds of polyoxyethylene withpolyoxypropylene, an alkyl radical of said non-ionic compoundspreferably having 5 to 20 carbon atoms; and as amphoteric surfactantsN-alkyl, N-dirnethyl betaine or l-hydroxyethylene-2-alkyl-2-imidazoline,an alkyl radical of said amphoteric compounds preferably having 5 to 20carbon atoms.

A mixture of at least two surfactants belonging to any one of the fourtypes (cationic, anionic, non-ionic and amphoteric types) is alsoemployed.

Furthermore, a mixture constituted of at least two different types ofsurfactants is often used, except the combinations of cationic type withanionic type or amphoteric type and of anionic type with amphoteric.type.

In the present invention, at least 1.5 weight percent of surfactant orsurfactants based on the product fiber in dry state must be absorbedinto an aquagel filamental fiber in a substantially unorientedcondition.

The absorption content will be preferable in the range of 1.5-6 weightpercent, although strictly speaking the chemical composition, molecularstructure and molecular weight of the surfactant to be used will alsodepend on the above mentioned eifects to some extent. The content in therange of 2.5-4.5 weight percent will be more preferable.

The present invention is effective when applied to the processes foracrylic fiber production in which an aqueous inorganic salt solutioncontaining zinc chloride or an alkali or alkaline-earth metal salt ofthiocyanic acid as a principal component is used as the solvent forfiberforming acrylonitrile polymer or copolymer. It will be moreeffective for the aqueous saline solvent of zinc chloride alone or of amixture of zinc chloride with a chloride of an alkali or alkaline-earthmetal, where the total salt concentration is preferably in the range of55 to 65 weight percent.

The acrylonitrile polymer employed in the present invention ispolyacrylonitrile and any of the acrylonitrile copolymers containing atleast weight percent of polymerized acrylonitrile and up to 15 weightpercent of other monomer or monomers copolymerizable with acrylonitrilesuch as methyl acrylate, methyl methacrylate, vinyl acetate, acrylamidestylene sulfonate, allyl sulfonate, methallyl sulfonate, acrylic ormethacrylic acid, itaconic acid, vinyl pyridines and vinyl imidazoles.

EXAMPLE 1 A spinning solution comprizing parts of saline solventcontaining 53 wt. percent zinc chloride, 4 wt. percent sodium chlorideand 43 wt. percent water and 10 parts of acrylonitrile copolymercomposed of 92 wt. percent acrylonitrile unit and 8 wt. percent methylacrylate unit was spun out through 6,000 holes spinnerets into acoagulating bath of an aqueous salt solution prepared by diluting thesaline solvent to 20 wt. percent concentration.

The aquagel tow withdrawn out of the coagulating bath was Water washeduntil substantially free of zinc chloride where it was drafted by 2.5times in the water baths to facilitate the washing. The washed aquageltow was immersed in an aqueous emulsion at 40 C. for 15 seconds whichcontained 30 grams per liter of diethanolamine mono-ester of lauric acidphosphate, squeezed with press-rollers and dried. The dried towcontained 1.5 wt. percent of the surfactant. The dried tow was thenheatstretched by 5.2 times at 0., immediately relaxed by 30% in a steamover-heated to 200 C., cooled and crimped. The tow thus obtained had 0.2wt. percent of the surface oil and 1.3 wt. percent of the inner oil.

The knitted goods made from the fiber thus obtained gave an excellenthand and had a high resilience comparable to that of wool goods.

7 Their excellent hand was negligibly changed even after several cyclesof their Washing and drying. Such were equal or comparable to those ofbulky sweaters or 100% wool.

TABLE 3 Sample No. 1 3 5 Amount of total oil in the fiber 0.36 wt. 1 wt.2 wt. 3.5 wt. 4.5 wt. Hand grade percent percent percent percent percentBest person 0 person... 1 person..." 8 persons. 1 person. Very good 0person... 0 person 3 persons 2 persons. 5 persons. (1ood 0 person 1person 5 persons 0 person 4 persons. Medium 3 persons... 6 persona... 1person 0 person"... 0 person. Bad 7 persons... 3 persons... 0 person 0person... 0 person.

good results could not be obtained for those made from EXAMPLE 3 theacrylic fibers having no detectable amount of the inner oil.

EXAMPLE 2 In the experiment A, the aquagel tow obtained under the sameconditions as those in Example 1 was water an aqueous dilute emulsion ofpolyoxyethylene alkylamine so as to have additional 0.1 wt. percent ofthe alkylamine on the fiber surface. The total amount of the surface oilcomposed of polyoxyethylene alkylamine and diethylaminoethyl oleic acidamide was 0.35 wt. percent in total based on the knitted goods made fromthe product were very much wool-like in hand.

On the other hand, in the experiment B, the washed aquagel tow obtainedunder the same conditions as those described above was stretched by 5.0times in hot water at 90-95 C., relaxed in boiling water, squeezed withpress-rollers, contacted with an aqueous emulsion containing 7 grams perliter of polyoxyethylene alkylamine and 7 gram per liter ofdiethylaminoethyl oleic acid amide for 2 seconds and squeezed again.This wet tow was, then, dried under a very weak tension accompanying afurther relaxation, subjected to heat-setting and a second oilingtreatment with the alkylamine and finally dried. In this process thetotal relaxation applied to the tow was controlled to be of the samepercent as that applied in the experiment A, and also the first andsecond oiling treatments were controlled so as to adjust the amount ofthe surface oil near 0.35 wt. percent in total. The product fiber had agood spinning property, but the knitted goods made from the fiber wereinferior in their quality to those made in the experiment A.

Five tow samples containing different amounts of the oiling agent wereproduced under the same experimental conditions as described above,except that the total surfactant concentration in the first oiling bathwas different for each sample making. From those'tows, the correspondingfive kinds of bulky sweaters were manufactured by applying the sameprocesses and under all the same conditions, where the bulky yarns weremade through Turbo process. For all the sweater samples, the knittingconstruction as well as the yarn count and shrinkage were all the same.A sensory inspection of the hand of those sweaters was carried out by 10persons having a lot of experience on the quality test of knitted andwoven goods. The statistical result shown in Table 3 was obtained, andan additional experiment showed that the Best and Very good gradesindicated in Table 3 9 weight parts of copolymer composed of 92 wt.percent acrylonitrile and 8 wt. percent methyl methacrylate weredissolved in 91 weight parts of an aqueous saline solvent comprising 42wt. percent zinc chloride, 16 wt. percent calcium chloride and 42 wt.percent water.

The polymer solution thus obtained was spun out through spinnerets intoa coagulating bath of an aqueous salt solution prepared by diluting thesaline solvent to wt. percent concentration. The aquagel tow withdrawnout of the coagulating bath was water washed countercurrently, squeezedand immersed in an oiling bath of aqueous emulsion containing 20 gramsper liter of dilauryl phosphate sodium salt, 20 grams per liter ofpolyoxyethylene stearic amide and grams per liter ofpolyoxyethylenepolyoxypropylene block polymer.

The aquagel tow was then dried, heat-stretched by 5.5 folds at 150 C.and then immediately relaxed, by percent based on the length of thestretched tow, in a steam overheated at 250 C. The resultant fibercontained 4.5 wt. percent in dry base of the surfactant. The knitted andwoven goods made from the above fiber were more excellent in theirhandling quality and anti-electrostatic property than those made fromacrylic fibers containing no detectable amount of any surfactant.

What we claim is:

1. A method for producing acrylic fibers from a spinning solution of anacrylic polymer comprising at least percent by weight of polymerizedacrylonitrile in an aqueous inorganic solvent comprising mainly zincchloride, said method comprising:

(a) spinning said acrylic polymer solution into an aquagel tow andwashing the resulting aquagel tow until same is substantially free fromresidual salt,

(b) treating the washed aquagel tow having a fiber structure which issubstantially in an unoriented state with an aqueous emulsion of atleast one surfactant selected from the. group consisting ofdiethanolamine mono-ester of lauric acid phosphate, polyoxyethylenelauryl amine, diethylaminoethyl stearyl amide, dilauryl phosphate sodiumsalt, polyoxyethylene stearic amide and a block polymer ofpolyoxyethylene-polyoxypropylene, at a temperature below 50 C. so as toimpregnate said washed aquagel tow with 1.5 to 6 weight percent of saidsurfactant based on the resultant dried fiber,

(c) subsequently drying the aquagel tow treated with said aqueoussurfactant emulsion at a temperature above 80 C. to irreversibly fixsaid surfactant in the fibrous structure, and then (d) heat-stretchingthe substantially dried tow over 4 times at a temperature between and180 C. and heat-relaxing the stretched tow with a superheated steam at atemperature of at least C. under atmospheric pressure.

(References on following page) References Cited UNITED STATES PATENTSWalter 264-182 Rouston et a1 264182 X Rouston et a1 264182 X Nakayama eta1. 264211 X Nakayama et a1. 264182 Jones et a1 264182 3,113,369 12/1963Barrett et a1 2528.6 3,129,273 4/1964 Lowes 264182 3,140,957 7/ 1964Kenichi Tanabe et a1. 264346 3,329,758 7/1967 Morgan et a1.

5 JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner US. Cl.X.R.

Elton et a1 252-88 10 1177; 264-130, 168, 182

